The present invention relates to covers for roller chain couplings, and more particularly to covers therefore used to retain lubricant at the coupling joint where misalignment is accommodated.
Roller chain couplings of the type with which the present invention is concerned typically include two identical steel coupling sprockets connected by a double strand of roller chain. The sprockets have axially extending hub portions for connection to substantially aligned shafts to transmit torque from one shaft to the other. Misalignment of the shafts is accommodated by the coupling through the double strand of roller chain.
Misalignment results in wear between the roller chain parts and between the chain rollers and the sprocket teeth. Typically, lubricant is applied to the roller chain to reduce such wear. As the speed of these couplings increases, the lubricant must be enclosed so that it will remain in contact with, and not be centrifugally thrown out of, the coupling.
Roller chain coupling covers have been found to suffer several drawbacks. Existing covers have been relatively rigid and manufactured from a rigid plastic or metal materials. Such covers comprise two semi-cylindrical halves that are fastened together after being placed over the coupling. Because of its rigidity, the cover requires a flexible seal at the location where the cover joins the coupling to retain the lubricant. The seals in such covers have proved inadequate in applications where misalignment caused the seal to wear unevenly resulting in the loss of lubricant from the interior of the cover. A second disadvantage associated with rigid covers is that the radial walls of the cover are spaced from the roller chain thereby allowing the lubricant to migrate away from the roller chain during operation of the coupling. Another disadvantage attributable to rigid covers is the relatively high cost associated with their manufacture and their multi-part construction.
Flexible covers have been used to retain lubricant in the flexing joints of universal joints and similar applications. However, covers of this type are also unsuitable for use with the roller chain couplings. Their flexibility allows the cover to expand radially during operation thereby allowing lubricant to migrate away from the roller chain where it is needed. Also, known covers of this type require the use of compression bands or other mechanical fastening means to secure the axial edges of the cover in place.